This invention relates to a method and apparatus for cyclically controlling the energization of water heaters on a daily and seasonal temperature basis to thereby reduce peak power demand on electrical utilities.
Electrical utilities generate electric power in three primary modes, that is, a base load, a mid-range load and a peak load. Characteristically, the base load is generated by nuclear power, large oil, coal and/or gas fired units. The present day cost of fuel averages about two mills per kilowatt for nuclear power, 11 mils per kilowatt for large base load oil, coal and gas units, 19 mills per kilowatt for mid-range oil, coal and gas units, and 22 mills per kilowatt for peak load gas turbine generators. Typically, base load generators are kept in continuous operation except for short maintenance intervals throughout the year. Mid-range units have their boilers fired on a continuous basis but the generators are on line when required. Peak power turbines are fired up only when necessary to meet peak load demands. Statistically, base load units now in service are capable of supplying 54% of power generated over 85% of the load demand cycle; while mid-range units are capable of supplying 25% of power generated over 25% of the load demand cycle and peaking units supply 21% of the power generated for a relatively short peak load demand interval which lasts approximately 8% of a daily load demand cycle. In a typical load pattern for a composite utility, i.e., a utility having a load demand characteristic which is the average of all utilities located throughout the country, the base load units carry the total load from midnight to 8:00 a.m., while auxiliary mid-range units typically must operate from 8:00 a.m. to midnight to provide additional required power and peaking units are typically operated from 12:00 noon to 9:30 p.m. to provide peak power as required. The use of these electricity generators for each separate utility will, of course, vary depending upon the locality of the utility and the method of power generation therein. It, however, does become obvious at this point that large utilities would prefer to generate as much power as possible by nuclear units and as little as possible by oil, gas or coal fired units because of the substantial difference in expense per kilowatt hour. However, only 5% of the nation's energy is presently generated by nuclear power and extended use of nuclear power is now in jeopardy due to malfunctions in nuclear plants now existing and because of environmental concerns. It therefore is likely that oil, coal and gas will remain the major source of generated electric power for at least another fifteen years. This means that electrical utility companies are going to continue to have great difficulty in providing relatively inexpensive electricity in the manner which they have been in the past. The continuous increase in the cost and the diminishing available quantities of fossil fuels taken together with the inability of using nuclear power plants on a continuous basis and the difficulty of building such nuclear power plants, the increased cost of capital, and the inability of utilities to attract capital investors, all add up to a need for an economical and reliable method and apparatus for reducing the demand at peak load intervals on electric utilities.
Approximately 33% of the total electric power generated in the United States is consumed in homes. Of the 69,000,000 homes served by electric utilities, approximately 20,000,000 use electric hot water heaters. These 20,000,000 homes consume an estimated 20% of the electrical power generated in homes. By far the largest consumer of electric power in homes which are not heated by electrical power is the electric water heater. These units when set at a temperature of 160.degree. F, as is typical, account for a minimum of 20% and in many cases as much as 50% of power consumed. The power consumption of electric water heaters can be cut in half without any inconvenience to the consumer if the energization thereof is appropriately controlled, thereby reducing peak power requirements in the home from 10% to 25%.
It is therefore an object of this invention to provide a method and apparatus for reducing power demand on electrical utilities.
It is another object of this invention to provide a method and apparatus for reducing peak power demand on electrical utilities.
It is yet another object of this invention to provide a reliable and economical method and apparatus for reducing both power and peak power demands on electrical utilities.